Brian is correct.
I think they are the same thing but I'm not 100%sure.
There aren't set definitions for these terms. Slab or rack just means they aren't cut apart. More important is whether they are Baby Back (the more tender, fattier portion near the spine) or Spare (chewier, leaner portion closer to the belly) or St. Louis, which are spare ribs plus a portion from the bottom of the ribs.
I think it's none.
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